Cannabis is a genus of flowering plants that includes three different species, Cannabis sativa, Cannabis indica, and Cannabis ruderalis. Cannabis has long been used for fiber (hemp), for seed and seed oils, and recently for medicinal purposes. In the mid-1930's, the growth of cannabis plants was outlawed in most countries due to its usage as a recreational psychoactive drug. In the 1970's, the ability to test and breed plants to contain low levels of the psychoactive drug, tetra-hydro-cannabinol (THC), became possible. Since this time, many countries have legalized the cultivation of cannabis plants that contain low THC content (0.3% or below). Unfortunately; during the period of prohibition; cultivation knowledge, processing equipment, and expertise had been optimized for other natural fibers, such as cotton, and synthetic polymer fibers, resulting in hemp not being economically viable.
Today, the growth and use of cannabis is extremely small and relegated to production of the seed for sale to the food industry. Recently, the growth of cannabis for use in the pharmaceutical industry has begun. Although not economically feasible to grow solely as a fiber source, the cannabis stalk (which is the fiber source) is a waste product when grown for the seed or for the compounds used by the pharmaceutical industry. Therefore, cannabis can be economically competitive as a fiber source when the stalks are harvested as a waste product from these industries.
The cannabis stalk (or stem) consists of an open cavity surrounded by an inner layer of core fiber, often referred to as hurd, and an outer layer referred to as the bast. Bast fibers are roughly 20% of the stalk mass and the hurd 80% of the mass. The primary bast fiber is attached to the hurd fiber by pectin, a glue like substance. Cannabis bast fibers have a large range in length and diameter, but on average are very long with medium coarseness; suitable for making textiles, paper, and nonwovens. The hurd consists of very short, bulky fibers, typically 0.2-0.65 mm in length.
Cannabis fibers are hydrophobic by nature. In order for them to be used for paper products, the fibers need to be liberated, typically by oxidation, in order to make them hydrophilic and suitable for use in fabricating paper using a wet laid process. In conventional cannabis fiber preparation, the cannabis fibers are pulped and bleached to remove the bound lignin and pectin and further separate the fiber bundles that still exist after decortication, the mechanical separation of the fibers in the cannabis stalk.
Conventionally, the pulping of cannabis is usually an alkaline process where the fibers are added to a digester under elevated temperature and pressure with caustic chemicals (e.g., sodium hydroxide and sodium sulfate) until all fibers are separated from each other. Washing with excess water removes the chemicals and the extracted binding components. The conventional pulping process removes the pectin from the cannabis fibers and requires a substantial amount of water when the fibers are added to the digester.